Optical modules with a box shaped package and lead terminals laterally extending from the sides of the box shaped package have been well known as, what is called, the butterfly module. Such butterfly modules emit light in a direction substantially in parallel to the bottom thereof. Even when the butterfly module implements a thermo-electric cooler (hereafter denoted as TEC) to control a temperature of a light-emitting device, typically a semiconductor laser diode (hereafter denoted as LD), the TEC may be mounted on the bottom of the module, because the light is extracted from a side of the module.
The butterfly module, in particular, the box shape package thereof is generally less preferable from viewpoints of cost and size factor thereof. As one of substitutions of the butterfly module, a multi-layered ceramic package widely used in electronic devices has been attracted. The ceramic package has not only the superior size factor but an advantage to form interconnections for high frequency signals. However, the, multi-layered ceramic package inherently provides a disadvantage that light is necessary to be extracted from the ceiling thereof and the heat generated therein is necessary to be extracted from the bottom thereof, that is, a direction along which the heat is conducted to the outside of the package is substantially in parallel with the optical axis thereof. The present application is to provide one of solutions to dissipate heat from the ceramic package effectively.